The disclosure of Japanese Patent Application No. 2001-260321 filed on Aug. 29, 2001 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of Invention
The invention relates to a control apparatus that automatically stops or starts an internal combustion engine, for example, a diesel engine, a gasoline engine and the like when a predetermined condition is established.
2. Description of Related Art
In consideration of a recent trend requiring reduced exhaust gas emission and improved fuel economy, it is recommendable to stop an engine of a vehicle rather than idle the engine when the engine is temporarily stopped. In such a case, a driver is required to stop and re-start the engine by manually operating a main switch or an ignition switch. However, the driver does not always implement the aforementioned operation for the stop and re-start of the engine. Technology has been developed for controlling the engine so as to be automatically stopped and re-started. This technology is a so-called economy running control or an eco-run control.
The exemplary eco-run control system is disclosed in JP-A-2001-88580. The disclosed system is designed to automatically stop and re-start an engine in a shifting state where torque is generated on an output shaft of a transmission by setting the shift lever at a drive range, such as a D-position. More specifically, a command to stop fuel supply to the engine is issued upon establishment of an engine stop condition. The engine stop condition includes, and not limited to, the following conditions: 1) the vehicle speed is equal to or lower than a predetermined value that approximates to zero; 2) a brake pedal is operated (in ON state); and 3) an accelerator pedal is released (in OFF state). Then a command for re-starting the engine is issued upon establishment of an engine re-start condition that includes, and not limited to, the following conditions 1) the accelerator pedal is operated; and 2) the brake pedal is released.
The aforementioned eco-run control (or a D-range eco-run control) is employed to stop the engine when the vehicle temporarily stops at a stop signal or the like during a travel to a destination. Accordingly it is required that the engine be re-started upon takeoff after the temporary stop of the vehicle without a delay. However, as various controls are performed from the start of the engine stop control until re-start of the engine, a delay in the start of the vehicle may make the driver irritated because of the sense of delay.
If the engine is stopped by merely stopping the fuel supply, the engine undergoes inertial rotation, during which torque is caused by compression pressure, resulting in vibrations. Such an event is likely to occur in diesel engines that involve high-pressure compression. Therefore, in order to smoothly stop the engine operation, the flow rate of intake air is required to be reduced by closing an intake throttle valve or an EGR valve (a valve for re-circulating exhaust gas to an intake side) so that a quantity of air introduced into each cylinder is reduced and the actual compression ratio is reduced, before stopping the supply of fuel.
The engine operation is not stopped immediately after the stop of the fuel supply but continues running by inertia. The engine speed gradually decreases until the engine finally stops. In order to re-start the engine subsequently, it is necessary to crank the engine. If the engine is cranked using a gear-type starter, it is necessary to determine whether the engine has been in a stopped state before engagement between the gear of the starter and a gear of the engine because those gears can be meshed in a state where the engine operation is stopped.
It is determined that the engine has stopped on the basis of an electric signal, for example, a pulse signal obtained by rotation of a rotating shaft such as a crank shaft. Due to the need to discriminate between a signal state caused by a stop of the engine and a signal state caused by a temporary reduction of the engine speed, the determination of the stop is made based on the continuation of the signal state for a predetermined time period. That is, determining whether the engine has stopped requires a certain amount of time in order to prevent a false determination.
After it is determined that the engine has stopped as described above, engine re-start control is executed by, for example, operating the starter, and re-starting fuel injection, etc., is resumed. Thus, after the stop condition is established, a preparatory control for stopping the engine, for example, a control for reducing the intake or the like, is performed. Then, the fuel supply is stopped so as to wait for a decrease in the engine speed. After the elapse of the time for the determination, the engine is restarted.
In the conventional control technology using a gear-type starter, in order to establish smooth gear engagement, the engine is re-started only when it is determined that the engine has stopped as described above. Therefore, even if the engine re-start condition, for example, depression of the accelerator pedal, is established (request for re-starting) immediately after establishment of the engine stop condition, the engine is not re-started. This is because the engine is re-started after an elapse of time taken for executing the engine stop control. As a result, the engine is re-started with excessive delay. When the request for re-starting the engine is issued immediately after establishment of the engine stop condition, the engine is re-started with a certain time lag, which makes the driver experience a sense of delay.
Accordingly, the invention thus provides a control apparatus of an internal combustion engine, which is capable of improving the response to a re-start of the engine that has been automatically stopped.
In an exemplary embodiment of the invention, when the request for restarting the engine is issued during a predetermined period prior to completing the start of the engine, the engine stop control is discontinued even if the engine stop condition is established. This makes it possible to allow the engine to be continuously operated without being stopped. In a control apparatus for an internal combustion engine, a stop control for stopping the internal combustion engine is executed when a predetermined engine stop condition is established. The stop control includes an operation to stop the supply of fuel to the engine. A re-start control for re-starting the internal combustion engine is executed when a predetermined engine re-start condition is established. The re-start control includes an operation to resume the supply of fuel to the engine. The stop control for stopping the engine is discontinued when the predetermined engine re-start condition is established during a predetermined period between establishment of the predetermined engine stop condition and stop of the internal combustion engine.
According to the aforementioned exemplary embodiment, establishment of the engine stop condition is followed by the engine stop control. In the case where the engine re-start condition is established during a predetermined period prior to the stop of the engine, the engine stop control for stopping the engine is discontinued. This may allow continuous operation of the engine without being stopped. Therefore, the engine is promptly operated in response to the establishment of the engine re-start condition without delay, avoiding the time lag in the response to the engine re-start control.
The predetermined period is a period taken for an engine stop preparatory control executed before the operation to stop the supply of fuel to the internal combustion engine so as to decrease a speed of the internal combustion engine.
In the exemplary embodiment, when the engine re-start condition is established in the state where the engine is operated at the decreasing speed, the engine stop control is discontinued. As a result, the engine is continuously operated without being stopped. The engine, thus, can be driven promptly in response to the establishment of the engine start control with no delay. The time lag in the response to the engine re-start control can be avoided.
The controller discontinues the stop control for stopping the internal combustion engine by controlling the internal combustion engine into a predetermined operating state where the engine starts rotating by itself.
In the aforementioned exemplary embodiment, when the engine stop control is discontinued, the operation state of the engine that has been changed until discontinuation of the engine stop control is recovered to the state prior to the engine stop control. As a result, autonomous operation of the engine can be continued.
The controller initiates re-start of the internal combustion engine when the internal combustion engine is stopped even after initiating the discontinuation of the control for stopping the internal combustion engine.
In the aforementioned exemplary embodiment, when the engine is stopped even if the engine stop control is discontinued during operation of the engine, the engine is immediately re-started. Start of the engine, thus, can be promptly executed upon establishment of the engine re-start condition. As a result, the delay in response to the engine starting control may be avoided or reduced.
The predetermined period is a period taken for decreasing an opening of a flow control valve at an intake side that is decreased before stopping the supply of fuel to a predetermined opening degree.
In the aforementioned exemplary embodiment, when the engine re-start condition is established during a period for which the opening of the flow control valve at the intake side is reduced to a predetermined value while supplying the fuel, the engine stop control is discontinued. As a result, the engine stop control is discontinued while keeping the intake operation. This may allow the operation of the engine continuously, thus improving the response to the control for re-starting the engine upon establishment of the engine re-start condition.
The predetermined period is a period taken for decreasing a speed of the internal combustion engine to a predetermined engine speed after stop of the supply of the fuel.
In the aforementioned exemplary embodiment, even after the fuel supply has been stopped the engine stop control upon establishment of the engine stop condition, the engine stop control may be discontinued so long as the speed of the engine is equal to or greater than a predetermined value. This makes it possible to have an autonomous engine operation by resuming the fuel supply to the engine. As a result, even after the engine stop control has been started upon establishment of the engine stop condition, the opportunity of autonomous engine operation upon establishment of the engine re-start condition may be increased.
The controller re-starts the supply of fuel after increasing the opening of the flow control valve at the intake side that has been decreased before stopping the supply of fuel.
In the aforementioned exemplary embodiment, in the case where the engine stop control is discontinued, the opening of the flow control valve at the intake side is increased before resuming the fuel supply. This makes it possible to have the engine autonomously operated reliably and smoothly.
The controller re-starts the supply of fuel when a speed of the internal combustion engine at a time when the opening of the flow control valve at the intake side is increased to a predetermined opening degree becomes equal to or higher than a predetermined engine speed.
In the exemplary embodiment of the invention, the supply of fuel is resumed upon discontinuation of the engine stop control if the engine speed obtained when the opening of the flow control valve at the intake side is increased to a predetermined value. This makes it possible to have the engine autonomously operated reliably and smoothly.